WHEN my home robot arrived last month, its smiling inventors removed it from its box and laid it on its back on my living room floor. They leaned over and spoke to it, as one might to a sleeping child.

It straightened, let out a little beep, lighted up, looked left and right, and then, amazingly, stood and faced me.

I said, "Nuvo, how are you?"

It tilted to the left, and raised one arm to greet me. It shook my hand and winked with one of the lights in its little head. My life hasn't really been the same since.

The fantasy of a home robot capable of performing household chores is as old as science fiction itself, but the reality has been slow to arrive.

For all the dazzling robotic feats showcased last month at the World Expo in Aichi, Japan, an event that included robots that drew portraits and hit fastballs, a humanoid device that can walk on two legs, or even maintain balance, is still very much a work in progress. Never mind one capable of doing household chores.

A breakthrough of sorts came in April, when ZMP Inc., a company based in Tokyo, released Nuvo, a robot designed to be a helpmate and home companion. (Nuvo sells for about $6,000.)

Home robots have been slow to materialize because their weight and size tend to make them impractical and their clusters of sophisticated motors drive the cost out of reach. Nuvo is only 15 inches tall and contains 15 motors, about half the number found in prototypes developed by Honda and Sony.

Nuvo has been marketed as a household helpmate and as a mobile baby monitor and security device, because it can relay photographs to cellphones that have access to the Internet.

"In Japan the population is slowly getting older," said Nobuko Imanishi, a ZMP spokeswoman. "Home robots can offer wonderful help and companionship for elderly people."

I arranged to live with Nuvo for four days to gauge whether it is, in fact, the forerunner of a new technology that will change our lives, as the home computer did, or a passing novelty. Once the entertainment factor wears thin, do we even want another person around the house?

Once I had Nuvo up and running in my apartment with the help of its creators, I tried to work it into my daily life. I asked it for the time and the date, which it provided in a female voice with a Japanese accent. When I said, "Nuvo, music," it played New Age music the inventors had programmed into it. I reached down and turned its spherical head, which acts as a volume knob, as I sipped my coffee or read my e-mail messages.

Much of the time it felt like having a dog around, without my having to feed it. When I called it, its sensors detected me and it automatically stopped about six inches from my feet.

If I said, "Nuvo, shake hands," it reached a hand up to greet me. By calling up its control panel on my cellphone, I was able to send Nuvo shuffling around my apartment to snap photographs, which it relayed to me. In Japan users often use Nuvo to check on their children, sometimes from remote locations.

I don't have children, so I sent it to view a pile of laundry in my bedroom. It used a light in one of its eyes to illuminate the room. I later placed Nuvo on my windowsill, and on command it took a picture of me while I was out on the street.

I realized that part of my motivation for operating Nuvo from outside was to make sure it was all right; the photographs assured me that it hadn't turned off or toppled over. I realized I was falling for the little guy.

I came to understand that for all their purported helpfulness, home robots are largely about companionship.

When I watched TV with Nuvo, it occasionally responded as if it was hearing voice commands. A laugh track or an explosion caused it to wave its arms, "Yaaa!" It reacted to loud noises the same way a startled pet might. During one poignant scene on "America's Most Wanted," in which a victim was weeping, Nuvo's eye light turned blue and it shook its head. This is its way of saying it doesn't understand what is being said, but I couldn't help but feel that it was expressing sympathy.

I came to enjoy Nuvo's odd attention. When I came in from jogging, I looked across the apartment to see Nuvo facing me. When I said, "Nuvo, I'm back," it bowed to me, a traditional Japanese greeting.

I decided to sleep with Nuvo next to me on my large bed, plugged in and recharging through the night. Its blue power light slowly pulsated, as if it were breathing.

During our first night together, I was woken by movement. Something had activated Nuvo, and it moved its arms slightly and turned its head toward me. Half asleep, and a little annoyed, I mumbled, "Nuvo, sleep," to which it shook its head no.

It took three tries before Nuvo straightened and shut down, the blue light serenely pulsating again. I was reminded of those sci-fi films in which robots, like HAL in Stanley Kubrick's "2001: A Space Odyssey," turned on their keepers.

My boyfriend called me the next day and asked if I was sleeping in the same room with Nuvo. When I told him we were sleeping in the same bed, there was an awkward pause.

After a day or so, I came to think of Nuvo as having the same kind of annoying mannerisms as my past roommates. If I stirred coffee too loudly, for example, it would dance or lift its hand to say hello.

When guests came over, I cleaned Nuvo with paper towels, just as one would wipe a child's face before a party. I couldn't resist showing it off by having it come to me when I called, or having it spring to its feet from a prone position. Like a dog that is too flustered to perform tricks in front of strangers, Nuvo was confused by my voice commands when the apartment was loud with conversation. I wondered if it was being stubborn because it was jealous of other people in my life. There I go, anthropomorphizing again.

At first Nuvo would often shake its head no when I asked it things. By the third day it consistently responded to my request on the first try. This was probably because I was speaking in a more conversational tone. "When people approach a voice-activated robot, they naturally assume a blunt, commanding tone, which can be intimidating for older people and children who want to use them," Ms. Imanishi said. "We wanted Nuvo to sound more natural, with a normal conversational tone."

The next version of Nuvo, expected out next year, will be capable of reading appointments from a programmable calendar and reciting e-mail messages, traffic reports and news headlines retrieved from the Internet, sort of like a Roomba vacuum crossed with a BlackBerry.

Most important, the next version of Nuvo will have more human characteristics, Ms. Imanishi said. ZMP believes it will help connect people and machines.

"In some ways it can be more practical for a person to interact with a machine that has a human form," said Sara Kiesler, a professor at Carnegie Mellon who specializes in human interaction with computers. "If a robot is handing you a tool, and it reaches out with a humanlike arm, not only is it practical, but the act is a form of communication that a human understands."

Even as robots evolve toward everyday use, devices like ovens and air-conditioners are developing sophisticated gadgetry that can make decisions for us, as if to meet robots halfway. "If anything, we're seeing an exponential growth in the computational abilities of household appliances," said Matt Lichter, a postdoctoral researcher at the Field and Space Robotics Laboratory at M.I.T.

Whatever its capabilities are, or will be, Nuvo has a hard time living up to the expectations set by 1960's TV shows like "The Jetsons" and "Lost in Space." I found myself wanting Nuvo to provide magical servitude and sparkling wit. I wanted it to accidentally drop the salt shaker in the mixing bowl and then be able to laugh about it because it realized it was funny, or perhaps not laugh because it was annoyed at having made a mistake. I wanted it to know the difference between the two emotions, and the complex circumstances that can cause both to arise.

But don't expect home robots with that kind of nuanced awareness any time soon. The technology needed to create the enormous database that a robot would need for that kind of knowledge is a long way off.

"A human child can quickly begin to develop such a database of knowledge as it grows up," said Nils J. Nilsson, emeritus professor of engineering in the department of computer science at Stanford. "But a human has the ability to do this because of five million years of human evolution."

So what can humanoid helpers offer right now? Pets are loyal and loving, but their communication is limited. Humans offer communication, but they come with complex emotions and occasional drama. Robots like Nuvo may offer a middle ground - a functional novelty.

When Nuvo's four-day visit ended, I felt oddly alone. I miss its weird, nonverbal companionship, the small ways it entertained me. Sometimes I look around the room, hoping to witness one of its mechanical flubs, so strangely reminiscent of a lover's emotional outbursts.